The present invention relates to an electromagnetic solenoid device for oil pressure control used for controlling power steering operation (oil pressure operation) of an automobile. More particularly, the present invention relates to such device for effecting a smooth movement of a movable iron core.
There has so far been known a device as shown in FIG. 1 which was published, for example, in Japanese Utility Model Publication No. 35009/1982.
In FIG. 1, a reference numeral 1 designates a solenoid device, a numeral 2 designates a solenoid coil, a numeral 3 designates a movable iron core (a plunger) capable of sliding in the direction of the arrow mark, a numeral 4 designates a push rod fixed to an end of the movable iron core 3, a numeral 5 designates a valve body (an oil pressure valve body) connected to the front end of the solenoid device 1, a numeral 6 designates a spool which is arranged in the valve body 5 and is moved in its axial direction of the valve body 5 by a pressure caused by the sliding movement of the movable iron core 3, a numeral 7 designates a spring bearing, a numeral 8 designates a spring and characters T, A and P designate oil pressure flow paths.
The operation of the solenoid device having the construction as described above will be illustrated.
When the solenoid coil 2 is actuated by current conduction from an external d.c. power source device, the movable iron core 3 is moved in the direction of the arrow mark to push the push rod 4. A pressing force of the push rod 4 is transmitted to the spool 6 and the spool 6 is caused to slide on the left hand in FIG. 1, pressing the spring 8. While the spool 6 is slidingly moved, the oil pressure flow paths T, A and P are changed.
In the conventional device constructed as abovementioned, since pressure oil (working oil) is filled in a receiving space for the movable iron core 3, a smooth sliding movement of the movable iron core 3 is prevented by pumping effect of the pressure oil.